FR2638109A1 - PROCESS FOR BINDING AND CONSOLIDATING SOLID AND LIQUID MATERIALS CONTAINING HEAVY METALS - Google Patents

Abstract

This process is of the type using a hydraulic binding agent at least latently. It consists in using a binding agent having the following characteristics: a) a siliceous component, hydraulic at least latently, coming from fly ash, combustion ash, slag or the like, with a particle size less than 100 mum, with a particle size less than 40 mum for at least 80% by weight, b) an alkaline and / or alkaline earth component, based on CaO, Ca (OH) 2, MgO, or Mg (OH) 2 as an activator of the component latently hydraulic, as well as c) calcium sulphide and / or calcium sulphate, anhydrous or in the form of hydrates, the ratio of the weight of component a) to the sum of components b) and c) being from 60 to 92: 8 to 40, and the content of component b) being from 3 to 5% by weight at least, this binding agent being mixed with the material to be treated, in a weight ratio of 20 to 60: 40 to 80, with a water content between 15 and 32% by weight relative to the substances allowing hydrate phases, then compri me and then hardened.

Description

PROCESS FOR BINDING AND CONSOLIDATING MATERIALS

  SOLIDS AND LIQUIDS CONTAINING HEAVY METALS

  WO 88/02739 discloses a method for bonding and consolidating materials containing heavy metals. In this context, the material to be treated is mixed with ash from a fluidized bed combustion and / or ash from the electrostatic precipitators of a plant, the ratio "water / substances allowing hydrate phases" being adjusted at a value

between 0.23 and 0.35.

  In principle, the known method has proved its worth:

  however, the binder content is generally

  more than 50% by weight, and the values of

  water mea sureness (k values) are limited to magnitudes

of the order of 10-10cm / s.

  In this context, the present invention aims to bind solid and liquid materials containing metals

  such as those encountered in the form of sub-

  products in waste incineration plants, special waste incineration plants, cleaning sludge, or similar places in an appropriate binding agent and to consolidate them, so as to obtain permeability values for water of solidified product lower than those known from the state of the art,

  this even for lower binding agent contents.

  In order to solve the problem, which is hereinafter described in more detail, the present invention advantageously utilizes the following knowledge: Unlike fly ash without additives,

  as used in WO 88/02739, the link

  and the solidification of residues containing heavy metals, but also those of organic residues, can

  be improved when the binding agent contains the compounds

  the following: - an at least latent siliceous, hydraulic component derived from fly ash, combustion ash, amorphous silicic acid, slag (eg slag sand) or the like, with a particle size of less than 100 μm, with a particle size less than pm for at least 80% by weight;

  an alkaline and / or preferably an alkaline

  earth-based CaO, Ca (OH) 2, MgO, or Mg (OH) 2 as an activator of the hydraulic component. latent as well as - calcium sulphate and / or calcium sulphide,

anhydrous or in the form of hydrates.

  Starting from a binding agent of such a composition, it has been found, moreover, that the desired result is obtained only when the weight ratio between

  the siliceous component and the alkaline / alkaline

  earthy alloyed with calcium sulphate and / or sulphide

  calcium, at a value of 60-92 to 8-40, the content of

  alkaline and / or alkaline-earth metal poses to be 3

at least 5% by weight.

  To the extent that, for example, fly ash already containing CaO is used; Ca (OH) 2R, MgO or

  Mg (OH) 2 free, we will add separately the component cor-

  respondent only proportionally. This applies

  calcium sulphate and / or sulphate

  calcium (if any, in the form of hydrates).

  In order to obtain the desired result, it is necessary

  need to carefully adjust the various components.

  The content of calcium sulphide and / or calcium sulphate binding agent should be between 3 and 25% by weight. Indeed; it turned out only for a lower content; the ability to leach heavy metals,

  as well as the permeability to water increase. The utilisa-

  higher concentrations of components containing sulphide or calcium sulphate leads to a decrease in the mechanical stability of the solidified products, since in this case it is observed. swelling phenomena causing bursting of the solidified body, as well as a detrimental increase in its lixivation ability. The minimum content of 3 to 5% by weight of alkaline and / or alkaline earth components is important insofar as it is a question of stimulating the hydraulic grip of the hydraulic component in a latent manner, of the binding agent,

  and at the same time to obtain a link in phases of hy-

  sufficient drafts, harmful substances.

  The latent hydraulic component produces, within the indicated binding agent, its effect, preferably. in the form of very fine particles, and therefore a particle size smaller than 100 μm and finer is proposed. preferably. The binding of metal ions

  in the hydrate phases obtained after the addition of

  water will be particularly intensive.

  By using the aforementioned binding agent, it is possible to bind in hydrate phases. solids as well as liquids containing heavy metals. In this context, the content of binding agent must be between 20 and 60% by weight and that of the

  material to be treated. between 40 and 80% by weight. If a

  in water from 15 to 32% by weight with respect to

  The processes involved in the formation of the hydrate phases make it possible to homogeneously mix the binding agent and the material to be treated. it also brings a total hydration of the reactive parts and a better binding of

heavy metal ions to be treated.

  It was surprising to find that by using the indicated binding agent in the amounts indicated, the

  values of water permeability (k values) are approximately

  In the case of many test mixtures, it has not even been possible to pass measurable quantities of water at a pressure of less than one to two powers of ten, less than those cited in WO 88/02739. bars through the completed samples. Similarly. the ability to leach ground products after setting was so minimal that it was well below the maximum amounts

  prescribed by law in the field of gold dumps

  (category II landfills, following the North Rhine-Westphalia draft directive). In most cases, even the quality requirements of the Austrian M 6250 standard for drinking water have

have been widely respected.

  If the time required for mixing

  of a material containing the heavy metal and the binding agent indicated depends in each case on the composition

  corresponding, it is usually located in a furnace

  from a few hours to a few days. After one week at the latest. solidification has reached a

  stage of completion allowing, without difficulty,

  the goods or to deposit them in a landfill, insofar as no prior

  removal and solidification at the scene of a

  charge. It is of course possible to add to the mixture composed of the material to be treated and the binding agent,

  generally known additions of nature. Among these addi-

  Examples include slag from metallurgical plants which, unlike slag sand, is non-hydraulic and will be introduced

  to the system as an inert addition.

  It has proved particularly useful to use

  use the calcium sulphide / calcium sulphate component of the binding agent. in the form of dry residues from spray absorption plants,

  these spray absorption installations function-

  with calcium oxide or aqueous solutions of calcium hydroxide or calcium carbonate and

  residues containing, besides calcium sulphide and sulphate

  calcium sulfate, if necessary in the form of hydrates, of the unused calcium hydroxide, which makes it possible

  to an equivalent extent, the quantity of the

  alkali and / or alkaline earth metal added separately.

  According to an advantageous embodiment of the method. it is proposed to use molten aluminous cement as an activator of the hydraulic component in a latent manner. Unlike conventional siliceous cement, such as portland cement, this cement consists mainly of calcium aluminates. It is used mainly as a binding agent for mortars and refractory concretes. To this extent, it must be surprising to note that the use of aluminous cement, preferably from 3 to 6% by weight, in the composition of the binder described, makes it possible to obtain, obviously

  through synergistic cooperation with other

  sants. values of lixivation ability and

  excellent water mea- surability and, in some cases, even higher than the values quoted above. In addition, it has been found advantageous to exclusively use latent hydraulic components having an SiO 2 content of at least 40% by weight. Fly ash

  mentioned, from combustion in central

  burning ash, slag or hydraulic slag

  latent (slag sands) are part of it.

  The binding agents obtained with these substances (without

  separate junction of amorphous silicic acid) contain for example 4055% SiO 2. 15-25% Al2O3, 5-30% CaO, and 3-12% SO3 / SO4 (all% indications are

data by weight).

  It should be distinguished from these ashes (agents

  hydraulic binders latently), ashes

  contaminated with harmful substances, such as ash from the incineration of waste, including the incineration of special waste. In these cases, the SiO 2 content is, in most cases, less than 40% by weight and sometimes even less than 10% by weight. As described above, it is possible to treat both

  solids as liquids. Among the

  such as, for example, sludge

  cleaning, materials loaded with heavy metals or

  organic substances. such as earth, heaps and flotation residues. etc. Among the liquid substances, there may be mentioned, for example, sewage from

  desulfurization of flue gases, wastewater

  industrial wastewater, municipal sewage and seepage water from landfills. By binding materials

  in the binding agent, the amount of water added separately

  can be reduced accordingly.

  To facilitate compression and reduce

  the ability to lixivate, one can add to the

  lange, liquefiers and / or sealants

  such as melamine resin, naphthalene sulphate, sulphate

  lignin fats, or silicones soluble in alcohol. The amount added in relation to the substances

  hydrate phases is between 0.2 and 3% by weight.

  The water content of the whole mixture is chosen, from

  preferably so that it is slightly above

  above the proctor value, the mixture being

  still at the limit of compressibility on an industrial scale. These measures lead to compression and reduction

  particularly advantageous capillary porosity.

  When the latent hydraulic component, of the binding agent, does not have a sufficiently fine granulometry, it will be ground separately. In this case, the grinding should make it possible to obtain particles of a size less than 10 μm directly. because it has been found that the binding of harmful substances can be further improved by increasing the fineness of the particles of the

  hydraulic component latently.

  Other features of the present invention

  derive from the following detailed description of

examples

EXAMPLE 1

  A mixture 1 was composed of a binding agent, composed of (all indications of% are given by weight):

  a) 80% ash of combustion (grain size less than

  less than 40 pm, of which 80% is less than 10 pm); b) 8% calcium oxide; c) 12% of dry residues from a Niro spray absorption plant operating with an aqueous solution of calcium hydroxide and comprising, in addition to 45% of component containing calcium sulphate / calcium sulphide, 55% of

  ash and free CaO. Ingrained particle size

less than 40 pm.

  % of this binding agent were mixed with 50%

  solid sidus from a waste incineration plant (ash / cake = 80/20%), with a water / substance ratio allowing hydrate phases, adjusted to 0.28. This mixture was then compressed. After completion of setting, the following compressive strengths were measured 28 days: 17 N / mm2 days: 25 N / mm2 180 days: 31 N / mm2 It was not possible to determine the value of the permeability to water (K value). that is to say, it was less than 1o-12cms. The value k has been determined

  analogically to the indications in DIN 18130.

EXAMPLE 2

  Mixture 2 was made analogously to

  described in Example 1. The binding agent was

  (all indications of% being given by weight): (a) 65% fly ash from a coal-fired power plant. with a particle size of less than 40 μm, of which 80% by weight also has a particle size of less than 10 μm; (b) 35% dry residues from a spray absorption plant, similar to

Example 1

  Component b). the component activator a) hydrau-

  latent, was contained proportionally already in the fly ash according to component a), with 18% of free CaO. Compared to the share of ashes

  0.6% of a lignin sulfate was added.

  Then. 30% of the aforementioned binding agent have been mixed

  70% dry residues from a special waste incineration plant (70% slag, 25% ash, 5% cake). The water / substances ratio

  allowing hydrate phases, was 0.32. The melange

  age was compressed. After completion of the setting, the

  The following compressive strengths were measured: 28 days t 14 N / mm 2 days: 23 N / mm 2 days: 33 N / mm 2 The value k in cm / s was initially still about 10%; after 90 days, it was impossible to determine. that is, it was less than 012; This test tube had a penetration of water still

  lower than that of the mixture according to the

  1. Given the impossibility of determining the

  their k. the penetration of water was measured according to

indications in DIN 1045.

Claims (12)

CLAIMS -   1. A process for binding and consolidating solid and liquid materials containing heavy materials,   using a hydraulic binding agent at least   tent, characterized in that, in order to obtain values of aptitudL at: ixivation as reduced as   possible and lower water permeability values.   used, a binding agent having the characteristics   following: (a) a siliceous, hydraulic component at least latent. from fly ash,   combustion ash, slag or the like.   of a particle size less than 100 μm, with a particle size of less than 40 μm for at least% by weight: b) an alkaline and / or alkaline-earth based CaO component. Ca (OH) 2.MgO, or Mg (OH) 2, as an activator of the latent hydraulic component as well as c) calcium sulphide and / or calcium sulphate, anhydrous or in the form of hydrates, the ratio of the weight of the component a) to the sum of the components b) and c) being from 60 to 92: 8 to 40, and the content of component b) being from 3 to 5% by weight at least,   this binder being mixed with the material to be treated, followed by   with a weight ratio of 20 to 60: 40 to 80, with a   water content between 15 and 32% by weight   substances that allow hydrate phases, then compressed, and then cured.   2. Method according to claim 1, the weight ratio of the component a) with respect to the sum of the components   b) and c) being adjusted to 60 to 80: 20 to 40.   3. Method according to claim 1 or 2, using a binder with a content of component c) included between 3 and 24% by weight.   4. Method according to any one of the claims   1 to 3. using as component c) of the binder, dry residues from an installation   spray absorption systems operating with   calcium hydroxide or aqueous solutions of calcium hydroxide or calcium carbonate, and containing, in addition to calcium sulphide and calcium sulphate, optionally in the form of hydrates, unpulse calcium hydroxide.   5. Process according to any one of the claims   1 to 4, using a component a) hydraulically latent, of a particle size largely lower at 10 pm.   6. Process according to any one of the claims   1 to 5, the component a) being replaced, in whole or in   partly by molten aluminous cement.   7. Process according to claim 6, using a quantity of molten aluminous cement of 3 to 6% by weight per   relative to the binding agent as a whole.   8. Process according to any one of the claims   1 to 7, using a component a) hydraulically la-   tent, whose SiO2 content is at least 40% by weight.   9. Process according to any one of the claims   1-8, using a binding agent containing silicon acid   and the chemical analysis in% by weight is as follows: Sio2: 40 to 80 A1203 5 to 45 CaO: 8 to 35 S03.S04 3 to 12   10. Process according to any one of the claims   1 to 9, adding a liquefier and / or a product of   to the binder compound mixture and to treat.   11. Process according to any one of the claims   1 to 10. the water content of the mixture being adjusted   to match the maximum compression possible ble during the proctor test.   12. Process according to any one of the claims   1 to 11, using as a heavy metal-containing material, filter dusts, filter residues from waste incineration plants, including waste incineration plants.   special waste, sludge, sludge   process liquids of SiO 2 content of less than 40% by weight, or similar materials.